TOKYO -- The bankruptcy filing by one of Japan's biggest retailers may signal that Prime Minister Junichiro Koizumi is finally starting the financial cleanup he promised. But it will take many more such steps before it is clear whether banks and the government really intend to clear away bad debt.

Mycal Corp., which operates super-markets and shopping centers, filed for protection from creditors under Japan's bankruptcy law late Friday. Its debts totaled 1.55 trillion yen ($13.22 billion) as of February 2001, according to...